Remove package ffpb-alfred-watchdog from site.mk

As A.L.F.R.E.D. v2013.x is known to crash in certain situations, we added the package to monitor the availabilty of the service on the nodes periodically in v0.5.3. It is said that these issues are resolved with A.L.F.R.E.D. v2014.x, which becomes available with the Barrier Breaker based release of Gluon (v2014.4). However, in contrast to Attitude Adjustment based releases, in which the script silently restarts the A.L.F.R.E.D. daemon, it will automatically issue an ffpb-debug report on Barrier Breaker (i.e. in v0.6.0). Hence, if there will not be notably many such reports after releasing v0.6.0, the package can be removed from site.mk with v0.6.1.